Methods of inhibiting corrosion with condensed polyalkylenepolyamine derivatives

ABSTRACT

WHEREIN R1, R2, R3, R4, R5, X and Y are hereinafter defined, n is 1-15 and m is 1-20, alone or in combination with zinc, dichromate, certain thiols and 1,2,3-triazoles and mixtures thereof, are disclosed as inhibiting the corrosion of metals by oxygen-bearing waters.   Condensed polyalkylenepolyamine derivatives having the formula

United States Patent King et al.

METHODS OF INI-IIBITING CORROSION WITH CONDENSED POLYALKYLENEPOLYAMINEDERIVATIVES Inventors: Thomas M. King, Creve Coeur;

Robert S. Mitchell, Webster Groves, both of Md.

Assignee: Monsanto Company, St. Louis, Mo.

Filed: June 30, 1972 Appl. No.: 267,871

Related US. Application Data Continuation-impart of Ser. No. 160,550,July 7, I971, Pat. No. 3,714,067,

US. Cl. 252/389 A, 21/25 A, 21/25 R, 21/27 A, 21/27 R, 210/58, 252/181,

252/855 E, 252/387, 252/389 R, 260/5025 Int. Cl C23f ll/l0, C23f 11/16Field of Search 252/389 A, 389 R, 181, 252/387, 8.55 E; 21/2.7 R, 2.7 A,2.5 R, 2.5 A; 210/58; 260/5025 References Cited UNITED STATES PATENTS12/1959 Ramsey et a1. 260/5025 Primary ExaminerLeland A. SebastianAssistant Examiner-Irwin Gluck Attorney, Agent, or Firm-Wayne R.Eberhardt ABSTRACT Condensed polyalkylenepolyamine derivatives havingthe formula wherein R R R R R X and Y are hereinafter defined, n is l15and m is 1-20, alone or in combination with Zinc, dichromate, certainthiols and 1,2,3- triazoles and mixtures thereof, are disclosed asinhibiting the corrosion of metals by oxygen-bearing waters.

19 Claims, No Drawings METHODS OF INHIBITING CORROSION WITH CONDENSEDPOLYALKYLENEPOLYAMINE DERIVATIVES This application is acontinuation-in-part of our copending application Ser. No. 160,550,filed July 7, 1971, now issued as US. Pat. No. 3,714,067.

The present invention relates to corrosion inhibiting compositions andto methods of inhibiting the corrosion of metal surfaces in contact withan aqueous medium of a corrosive nature. More particularly, thisinvention relates to methods of inhibiting the corrosion of metalsurfaces by utilizing in the corrosive aqueous medium a condensedpolyalkylenepolyamine derivative either alone or in combination with awater-soluble zinc salt, a dichromate, certain thiols, 1,2,3-triazolesand mixtures thereof. I

The present invention has special utility in the prevention of thecorrosion of metals which are in contact with circulating water, thatis, water which is moving through condensers, engine jackets, coolingtowers, evaporators or distribution systems, however, it can be used toprevent the corrosion of metal surfaces in other aqueous corrosivemedia. This invention is especially valuable in inhibiting the corrosionof ferrous metals including iron and steel (also galvanized steel) andnon-ferrous metals including copper and its alloys, aluminum and itsalloys and brass. These metals are generally used in circulating watersystems.

The major corrosive ingredients of aqueous cooling systems are primarilydissolved oxygen and inorganic salts, such as the carbonate,bicarbonate, chloride and/ or sulfate salts of calcium, mganesium and/orsodium.

It is, therefore, a primary object of this invention to provide newcorrosion inhibiting methods.

lt is another object of this invention to provide new corrosioninhibiting methods for ferrous metals including iron and steel andnon-ferrous metals including copper and brass.

It is another object of this invention to provide new and corrosioninhibiting methods for ferrous metals including iron and steel andnon-ferrous metals including copper and brass in contact with an aqueouscorrosive medium.

lt is another object of this invention to provide new corrosioninhibiting methods for ferrous metals including iron and steel andnon-ferrous metals including copper and brass in contact with coolingwaters.

Other advantages and objects of the present invention will be apparentfrom the following discussion and appended claims.

It has been found that certain condensed polyalkylene-polyaminederivatives corresponding to the following formula certain thiols andl,2,3-triazoles and mixtures thereof in aqueous or water systemscontaining metals or in contact with metals.

In the Formula 1, R R R and R are alike or unlike and are from the groupof radicals with the proviso that at least one C(X)(Y)PO M group ispresent at all times and is R R R or R In formula 1, R is an alkyl groupcontaining from 1 to 20, preferably 1 to 8 carbon atoms such as methyl,ethyl, propyl and the like.

In formula I and (partial) Formula II, X and Y are each alike or unlikeand are from the group hydrogen and alkyl containing from 1 to 8,preferably 1 to 4 carbon atoms.

In formula I, n has a value of from 1 through 15 and m is from 1 through20.

In formula I and (partial) Formula II and III, M is a metal ion orhydrogen or any cation which will yield sufficient solubility for thedesired end-use. The afore mentioned metal ions are from the group ofmetals alkali metals such as sodium, lithium, potassium, alkaline earthmetals such as calcium and magnesium, aluminum, zinc, cadmium,manganese, nickel, cobalt, cerium, lead, tin, iron, chromium, andmercury. Also included are ammonium ions and alkyl ammonium ions. Inparticular, those alkyl ammonium ions derived from amines having a lowmolecular weight, such as below about 300, and more particularly "thealkyl amines, alkylene amines, and alkanol amines containing not morethan two amine groups, such as ethyl amine, diethyl amine, propyl amine,propylene diamine, hexyl amine, 2-ethylhexylamine, N-butylethanol amine,triethanol amine, and the like, are the preferred amines. It is to beunderstood that the preferred metal ions are those which render thecompound a water-soluble salt, e.g., sodium.

It is to be understood that all of the compounds falling within theabove Formula I and as heretofore defined are generically describedherein as polyamine or polyamines. In other words then, the acids, saltsand mixtures thereof are all generically described herein as polyamines.

Illustrative (but without limitation) of some of the present inventioncorrosion inhibitors are shown below.

Compound No. R R R; R R X Y n m l -CH PO H -CH PO H- -CH, -CH PO H-CH,PO5H H H 3 l 2 do. do. do. do do. do. do. 6 l 3 do. do. do. do. do.do. do. 12 l 4 do. do. do. do. do. do. do. 3 8 5 do. do. do. do. do. do.do. 3 l5 6 -CH,CO0H -CH COOH -CH do. do. do. do. 3 l 7 do. do. do. do.do. do. do. 6 1 8 do. do. do. do. do. do. do. 12 l 9 do. do. do. do. do.do. do. 3 8 l0 do. do. do. do. do. do. do. 3 15 l l -CH PO H -CH PO -,H-Cl-l -CH,COOH -CH,COOH do. dov 3 I I2 do. do. do. do. do. do. do. 6 1l3 -CH CH OH CH CH OH CH -CH PO -;H -CH P0 H do. do. 3 l 14 do. do. do.do. do. do. do. 6 1 l5 do. do. do. do. do. do. do. 12 8 l6 do. do. do.do. do. do. do. 3 l5 I? do. do. do. do. do. do. do. 3 1 l8 -CH PO H, CHPO H -C H -CH CH OH -CH CH OH do. do. 3 1 I) do. do. do. do. do. do. do.6 l -CH P0;,Na -CH,PO:,Na -CH;,H 7 -CH PO Na CH PO Na do. do. 3 1 2| do.do. do. do. do. do. 6 l 22 -CH PO (NH,) -CH,P0,(NH, cu, or-130 mm), -CHPO (NH,) do. do. 3 1 23 V CH Po zn CH PO Zn CH 7 CH PO Zn CH PO Zn do.d0. 6 l 24 v CH COONu CH- COONu CH CH-zPOsNflz CH PO;,Na do. do. 3 l 25-z rl z CHQPOHHZ CH3 C :I 2 do. do. I5 20 utilized in the corrosivemedium. It is to be understood that greater than 500 ppm of polyaminecan be utilized where one so desires as long as the desired end resultis substantially achieved or these higher amounts are not detrimental tothe water system. Amounts as low as 1 ppm are found to be effective.

The polyamine corrosion inhibitors of the present invention areeffective in both .an acidic or basic corrosive media. The pH can rangefrom about 4 to about 12. For example, compound No. 1, heretofore setforth, when used in amounts from about 3 parts per million to about 100parts per million is an effective corrosion inhibitor in a corrosivemedium where the pH is from about 4 to about 12.

In conjunctior iwith the utilization of the polyamine per se ascorrosion inhibitors, it has also been found that there exists asynergistic effect on corrosion inhibition between the polyamine and thezinc ion; that is, the use of the polyamine with the zinc ion moreeffectively inhibits corrosion than does an equal concentration of thepolyamine or the zinc ion alone. (The zinc ion is used in approximatelythe same molar concentration as the polyamine, e.g., a suitablecorrosion inhibitor may consist of 10 ppm of zinc ion plus 50 ppm ofsaid polyamine.) It is to be understood, then, that the presentinvention also encompasses a corrosion inhibition composition containinga mixture of the polyamine and a zinc-containing material (i.e., awater-soluble zinc salt) which is capable of forming the zinc ion in anaqueous solution.

Illustrative examples of the zinccontaining material (water-soluble zincsalt) which are set forth for exemplary purposes, only and hencenon-restrictive, include zinc acetate, zinc bromate, Zinc benzoate, zincborate, zinc bromide, zinc butyrate, zinc caproate, zinc carbonate, zincchlorate, zinc chloride, zinc citrate, zinc fluoride, zinc fluosilicate,zinc formate, zinc hydroxide,

zinc d-lactate, zinc laurate, zinc permanganate, zinc nitrate, zinchypophosphite, zinc salicylate, zinc sulfate and zinc sulfite. Thepreferred water-soluble zinc salt is zinc sulfate. It is to beunderstood that it is within the scope of the present invention that thezinc ion can be supplied in part or wholly by using the zinc salt of theacid form of the polyamine.

The polyamine and the zinc containing material, which is, in essence, awater soluble zinc salt, may be mixed as a dry composition and can befed into a water system containing the metals heretofore described to beprotected. Such a composition having maximum synergism between thepolyamine and the zinc ion containing material comprises from about 2%to about by weight of the water soluble zinc salt and from about 20% toabout 98% by weight of the polyamine, all weights being predicated uponthe total weight of the mixture. Preferably the weight of thecomposition comprises from about 10% to about 60% by weight of the watersoluble zinc salt and from about 40% to about by weight of thepolyamine.

A combination of about 3 to 100 ppm of the polyamine and about 0.5 toabout 100 ppm zinc ion will inhibit corrosion in most water systems; themost preferred concentration range is about 5 to 25 ppm polyamine andabout 5 to 25 ppm zinc ion. It is to be understood, however, that thoseconcentrations are not in any manner meant to limit the scope of thepresent invention.

7 It has also been found that synergism exists between the polyamine andchromate or dichromate. Because chromate and dichromate are each readilyconverted into the other by a change in pH, it is understood that bothwill be simultaneously present at most pHs, even though only one ismentioned.

Corrosion is most water systems may be inhibited by adding from about lto about 100 ppm of polyamine and from about 1 to about 100 ppm of thechromate or dichromate; preferably from about 5 to 25 ppm polyamine andfrom about 5 to 25 ppm chromate or dichromate is added. It is to beunderstood that larger amounts or smaller amounts of each material canbe utilized if one so desires.

Suitable chromates for use in the composition and process of thisinvention include, for exemplary purposes only, sodium dichromatedihydrate, anhydrous sodium chromate. sodium chromate tetrahydrate,sodium chromate hexahydrate. sodium chromate decahydrute. potassiumdichromate, potassium chromate, ammonium dichromate, and chromic acid.lln other words, the chromium compound used is any water solublehexavalent compound of chromium and is preferably an alkali metalchromate or dichromate heretofore described.

In most cases, an effective corrosion inhibition composition contains amixture of from about 1% to about 60% and preferably from about to about40%, of the water soluble inorganic chromate, based on the combinedweight of the chromate and polyamine. The use of chromates per se isfurther described in U.S. Pat. No. 3,431,217 and the publications citedin this patent, all of which are incorporated herein by reference.

It has also been found that compositions of the polyamine, zinc ion, andchromate or dichromate are useful in inhibiting the corrosion of metals.The inhibiting action of Zinc (supplied in the form ofa water solublezinc salt heretofore mentioned) and dichromate compositions has beenshown in U.S. Pat. No. 3,022,133, which is incorporated herein byreference. Thus, all three components of this composition are mutuallysynergis' tic. The coaction of zinc and dichromate illustrated in U.S.Pat. No. 3,022,133 remains unaffected in the presence of the polyamineand the other ingredients of the inhibitor compositions mentionedherein. In other words, then, it is within the scope of the presentinvention to provide a corrosion inhibiting composition containing thepolyamine, a water soluble zinc salt and a chromate and/or dichromate.

Especially useful combinations of polyamine, chromate and zinc exist inthe range of from about 1 to about 100 ppm of polyamine, from about /2to about 50 ppm of the chromate or dichromate, and from about V2 to 50ppm of the zinc ion. The preferred range is from about 2 to 30 ppmpolyamine, and from about 1 to ppm chromate or dichromate, and fromabout 1 to about 15 ppm zinc ion.

Where the water systems are in contact with copper per se orcopper-containing metals, it is desirable to use, along with thepolyamine (either alone or in combination with the zinc ion and/ordichromate or chromate), a l,2,3-thiazoles or a thiol of a thiazole, anoxazole, or an imidazole as described respectively in U.S. Pat. Nos.2,941,953; 2,742,369; and 3,483,133; all of which patents areincorporated herein by reference. These azoles are referred to herein asthiols and 1,2,3- thiazoles. These thiols and 1,2,3-thiazo1es are foundeffective in inhibiting the attack of the polyamine on copper.

The preferred 1,2,3-triazole is 1,2,3-benzotriazole of the formula \N llThe preferred thiols of a thiazole, an oxazole, or an imidazole are2-mercaptothioazole 2-mercaptobenzothiazole 2-mercaptobenzoxazole Theamounts of thiol or 1,2,3-thiazo1e used will depend upon the particularwater system. Where the water system containing copper is an open oronce through system from about 3 to about 100 ppm polyamine, about 0.05to 5 ppm thiol or 1,2,3-triazole, and up to about 100 ppm zinc ion aregenerally satisfactory concentrations; preferably the concentrations areabout 5 to 25 ppm polyamine, about 0.5 to 2 ppm triazole or thiol, andabout 5 to 25 ppm zinc ion.

A dry composition may be made which may be fed into the water systemcontaining copper. Such a composition would consist of about 20% topolyamine; about 1% to 10% thiol or 1,2,3-triazole, and up to about 79%soluble zinc salt; preferably, it would consist of about 38% to 90%polyamine, about 2% to 10% thiol or 1,2,3-tria2ole, and up to about 60%soluble zinc salt.

It is within the scope of the present invention that the corrosioninhibitors of this invention may be used in conjunction with othermaterials (water treating chemicals); in some instances, there can be acooperative effect therebetween. The following is a list of thesematerials and publications wherein such materials are utilized in asimilar fashion in conjunction with corrosion inhibition.

1. Water-soluble polycarboxylic acids from the group adipic, succinic,azelaic, suberic, sebacic, pimelic, and glutoric acids and hydroxypolycarboxylic acids having from 4 to 10 carbon atoms and at least 2carboxylic acids or an alkali metal or ammonium salt thereof-noteBritish Pat. No. 1,230,172;

2. Acetodiphosphonic acids and salts thereof-note German Pat. No.2,115,427;

3. Lignins, lignosulphonate, starch, sodium mannuronate, agar-agar,polyelectrolytes which contain the group o o n in which R is nitrile,amide, carboxyl or carboxylalkyl and which have a molecular weight of5,000 to 15,000,000 and water-soluble salts thereof-note U.S. Pat. No.3,547,817;

4. Amino tri(methyl phosphonic acid) and monoand poly-phosphonicacids-note U.S. Pat. No. 3,510,436;

5. Polyacrylic acid, polyacrylamide or partially hydrolyzedacrylamidenote U.S. Pat. No. 3,505,238;

6. Aminomethyl phosphonic acid compounds such as those described in U.S.Pat. No. 3,483,133;

7. Derivatives of methanol phosphonic acid or methanol diphosphonicacids such as those described in U.S. Pat. No. 3,532,639;

8. The phosphorus-containing polar organic liquids described in U.S.Pat. No. 3,637,790;

9. Leucocyanidin catechin polymers, carbamates and sodium bisulfatewhich are described in U.S.

Pat. No. 3,518,203;

10. Lignosulfonate mixed sugar aldonate polymeric materials such asthose described in German patent publication No. 2,123,808;

1 1. Ethylene oxide-propylene oxide polymeric corrosion inhibitioncompositions containing phosphates, borates, nitrites, silicates andbenzoates such as described in German patent publication No. 2,054,506;

12. l-hydroxy ethylidene-l,l-diphosphonic acid and water-solubleorthophosphates such as those described in British Pat. No. 1,243,347;

13. A water-dispersible tannin compound and a HCN modified lignosulphateand/or an l-lCN modified naphthalene sulphonate such as those describedin British Pat. No. 1,244,123;

14. Silicate materials such as those described in U.S.

Pat. No. 3,630,930;

l5. Polyfunctional phosphated polyol esters such as those described inU.S. Pat. No. 3,580,855;

16. Sulfonated lignites such as those described in -U.S. Pat. No.3,629,105;

17. The polyphosphonic acids such as those described in U.S. Pat. No.3,619,427;

18. Molecularly dehydrated phosphates and phosphonates such as thosedescribed in U.S. Pat. No. 3,483,133;

19. Molybdates such as those described in An Electrochemical Study ofHeteropoly Molybdates as Cooling Water Corrosion Inhibitors, A.Weisstuch and C. E. Schell, Paper No. 104 presented at the March, 1972annual meeting in St. Louis, Mo. of the National Association ofCorrosion Engineers (NACE).

20. Inorganic Phosphates including orthophosphates.

3,617,578; 3,620,974 and 3,644,205. 25. And mixtures of the abovematerials listed in items 1 through 24. All of the above publicationsare to be considered as incorporated herein by reference.

In conjunction with the Examples hereinafter set forth, two tests areconducted to determine the effectiveness of the corrosion inhibitors ofthe present invention in different corrosive media, i.e., ordinary tapwater and synthetic cooling tower water.

Test 1 was conducted at room temperatures, about F, wherein severalcoupons of mild steel (S.A.E 1018) having dimensions of 5 cm X 3.5 cm X0.32 cm were thoroughly cleaned using a commercially available cleansingpowder and rinsed with distilled water and acetone. After the couponswere weighed, they were mounted on brackets and continuously immersedand removed from the corrosion composition, i.e., ordinary tap water, sothat the coupons remain immersed in the composition for 60 seconds andthen remained out of solution, exposed to air for 60 seconds. Thisprocedure was continued for a definite length of time (in hours) afterwhich the coupons were withdrawn and the corrosion products on thecoupons were removed by using a soft brush.

The coupons were rinsed with distilled water and acetone and thenreweighed. The loss in weight (in milligrams) was then appropriatelyinserted into the equation:

KW/DAT Corrosion in mills per year wherein W weight loss during tests inmilligrams;

D specific gravity of the metal;

A exposed surface area in square cm; and

T time of exposure to solution in hours K 3402 in order to determine thecorrosion that has taken place expressed in terms of mills ofpenetration per year (m.p.y.). The corrosion rate of the couponsprotected by a corrosion inhibitor can then be compared to the corrosionrate of the unprotected coupons. A decrease in the corrosion rateindicates the effectiveness of the corrosion inhibitor.

1n tests of this nature where the aqueous corrosive medium is ordinarytap water at room temperature, any corrosion rate less than thatcorrosion rate of the said medium is desired and rates of less than 5m.p.y. are highly desired and substances that give this value or lowerare considered excellent. This does not mean, however, that substanceshaving a corrosion rate of more than 5 m.p.y. are not valuable;depending upon the particular conditions a compound having a highercorrosion rate may be used, as in an instance where the equipment willbe used, only for a short period of time.

A cooling water system was constructed on a small scale to approximateactual conditions for Test 2. From a five gallon glass tank containingsynthetic cooling water, a hose leads into a 6 in. glass jacket whichsurrounds a mild steel pipe. A hose leads from the jacket into a glasscondenser and then back to the tank. Air is added to the system at thecondenser in order to match an actual operation in which air is absorbedby the cooling water. Steam is passed through the steel pipe which isenclosed by the glass jacket.

Four mild steel coupons were weighed and then mounted in the tank. Afterexposure the steel pipe was checked visibly for signs of corrosion andthe corrosion rate of the coupons was calculated. Synthetic coolingwater was prepared to approximate actual cooling water as follows:

(1 200 ppm Mg 55 ppm Na 320 ppm Cl 600 ppm 50, 500 ppm HCOfl' 58 ppmTotal Dissolved Solids of Distilled Water L733 ppm A circulating coolingwater system contains a high concentration of inorganic salt or ionsmuch higher than ordinary tap water as can be seen from the formulationfor synthetic cooling tower water. Likewise a cooling water system isoperated at high temperatures usually 50C or higher. Primarily becauseof these two factors the acceptable corrosion rates in cooling waters isless than 10 m.p.y. therefore, corrosion inhibitors having corrosionrates less than 10 m.p.y. are considered good and commerciallyacceptable.

The corrosion inhibiting compositions of this invention can bemanufactured via a number of methods which will give good protectionagainst corrosion. For example, the polyamine either in the form of itsacid or salt per se or in combination with the water-soluble zinc salt,chromate, dichromate, thiols and 1,2,3- thiazole can simply be dissolvedby intermixing them into the aqueous corrosive medium. Via anothermethod, they can be dissolvedseparately in water or another suitablesolvent and then intermixed into the aqueous corrosive medium.

Various means are available to insure that the correct proportion ofcorrosion inhibitor is present in the corrosive medium. For example, asolution containing the said corrosion inhibitor can be metered into thecorrosive medium by a drip feeder. Another method is to formulatetablets or briquettes of a solid" polyamine (and other ingredients) andthese can then be added to the corrosive medium. The said solid, afterbriquetting, can be used in a standard ball feeder so that the solid isreleased slowly into the corrosive medium.

The invention will be further illustrated but is not limited by thefollowing examples:

EXAMPLE l Three separate portions consisting each of 600 ml of aqueouscorrosive medium are individually treated with the indicated polyamineso that it contains separately 5, 50 and 100 parts per million ofpolyamine. (Where the acid form is used, it is converted to the sodiumsalt by the addition of sufficient NaOl-l to maintain the medium at pH9.0 to 9.5.) Test 1 as described hereinbefore is conducted using 1018S.A.E mild steel coupons measuring cm X 3.5 cm X 0.32 cm. The corrosivemedium is a sample of water obtained from the St. Louis County WaterCompany having a pH from about 9.0 to about 9.5 and a hardness of about100 to about 1 parts per million as calcium carbonate. Test 1 isconducted according to the procedure hereinbefore outlined for 90 hours.Six hundred ml. of the untreated aqueous corrosive medium is tested as acontrol. The data are illustrated in Table 1.

Test 1 is also conducted on a commercially available corrosioninhibitor, containing some zinc about 1 to about 4% by weight but mostlytetra sodium pyrophosphate about 40 to about 60% by weight; these dataare shown in Table 1.

TABLE 1 Corrosion Rates on Mild Steel (S.A.E. 1018) Coupons 5 cm X 3.5cm X 0.32 cm pH 9.0 to 9.5 of the Corrosive Media ll ilt ConcentrationTime Corrosion Corrosion Inhibitor ppm (hrs) Rate (m.p.y.)

Corrosion Medium 96 25.2

Polyamine Compound No.

l 5 96 8.1 l 96 4.7 1 I00 96 2.2 2 5 96 10.] 2 5O 96 8.4 2 I00 96 5.2 45 96 4.7 4 50 96 2.6 4 I00 96 2.0 6 5 96 9.7 6 5O 96 4.4 6 100 96 3.8 135 96 l l5 I3 50 96 5.0 I3 100 96 4.2 18 5 96 6.9 [8 50 96 3.9 18 100 963.0 20 5 96 8.2 20 50 96 4.6 20 100 96 2.8 22 5 96 l 1.3 22 50 96 6.3 22100 96 3.4

Corrosion Medium 96 29.6

Zinc Tetra Sodium Pyrophosphate (Zinc 1% 5 96 15 4%, tetra sodium pryo-50 96 6.8 phosphate 40% to I00 96 4.]

The data in Table 1 show that the polyamines are an effective corrosioninhibitor. Table 1 shows that these polyamines are at least as good asand in some cases superior to the commercially available zinc tetrasodium pyrophosphate inhibitor. As pointed out before, substances thatreduce the corrosion rates of mild steel to less than 5 m.p.y. inordinary tap water are considered excellent. Therefore, it can readilybe appreciated that the polyamines of the present invention areeffective corrosion inhibitors.

EXAMPLE ll Test 2, as described hereinbefore, is conducted to de*termine the effectiveness of the indicated polyamine (Example I) as acorrosion inhibitor in cooling water. The polyamines are added to thefive gallon tank containing about 16,000 ml. of synthetic cooling towerwater (having a flow rate of 2,640 ml./min.), as set forth above, sothat said water contains 5, 50, and 100 .parts per million of thepolyamine. The temperature of the synthetic cooling water is 50C. Mildsteel coupons (ASTM A-285) measuring 2.5 cm X 5 cm X 0.6 cm are cleanedwith a commercially available cleansing powder and weighed. They arethen mounted on brackets in the five gallon tank. After exposure, theyare re- Weighed and their corrosion rates are calculated.

A blank solution containing no polyamine is used as a control todetermine the corrosion rates of mild steel coupons in untreatedsynthetic cooling tower water.

The data show that the polyamine corrosion inhibitors at greater than 50ppm reduce the corrosion rate to less than 10 m.p.y. (the controlcorrosion medium is about 24.6 m.p.y.), which is the generallyacceptable rate for a corrosion inhibitor.

A visual inspection of the mild steel pipe through which the steampasses and which is cooled by the synthetic cooling water treated withpolyamine shows a very minute amount of corrosion, another indication ofthe effectiveness of the novel compound of the present invention.

1 1 A commercial corrosion inhibitor containing 2% to 4% by weight ofzinc and 40% to 60% by weight of tetra sodium pyrophosphate, is used totreat the synthetic cooling water and is tested in the same manner asExample II. The corrosion rates of the coupons are more EXAMPLE IIIExample I (above) is repeated with the exception that in addition to thepolyamine (5, 50 and 100 ppm) corrosion. inhibitor, there is addedsufficient amounts of zinc sulfate in order to provide respectively 5,50 and 100 ppm of zinc ion in the corrosion medium. The synergisticcorrosion inhibitor, i.e., the indicated polyamine plus the zincsulfate, shows that at all three concentrations (i.e., 5, 50 and 100 ppmof each) the corrosion rates are substantially less than the rates usingthe corrosion medium without this mixture and is on the average 25% lessthan those rates obtained using only the polyamine per se.

' EXAMPLE IV EXAMPLE V A series of separate and individual corrosioninhibitors consisting of a mixture of the indicated polyamine (60% byweight), zinc sulfate (20% by weight) and sodium dichromate (20% byweight) are prepared. Example I (above) is then repeated utilizing theabove mixture. The resultant data shows that the corrosion rates usingthis mixture are substantially less than the rates using the corrosionmedium without this mixture and is on the average about 31% to 41% lessthan those rates obtained using only the polyamine per se.

EXAMPLE VI The corrosion inhibitors as described in the above ExamplesI, III, IV and V are separately and individually tested in boiler waterfor their separate corrosive inhibiting effect on red brass and mildsteel. The boiler water contains approximately 30-60 parts per millionphosphate and approximately 30-60 parts per million sulfate having a pHof about '14. The corrosive tests are carried out at a temperature of314C at 1500 psig and with a 50 parts per million of the respectivecorrosion inhibitor. In each test, approximately 1 liter of boilerblow-down water is charged into a 2 liter bomb and 1 ml. of a stocksolution is added to give approximately 50 parts per million of thecorrosion inhibitor. Duplicate coupons of mild steel and red brassmeasuring 5 cm X 3.5 cm X 0.32 cm are scrubbed with a commerciallyavailable cleansing powder and weighed. The coupons are then mounted oninsulated brackets so that two coupons are in the liquid phase and twocoupons are in the vapor phase. After sealing the bomb, the cycle ofpumping down with a vacuum pump and filling with nitrogen is repeatedfour times. The time of the tests are taken to be roughly from the timethe temperature reached C after starting to heat till it again reachedthis temperature after turning off the heat.

The results of these tests show that at temperatures above 300C therespective corrosion inhibitors significantly reduces the corrosionrates of both red brass and mild steel either completely immersed in thecooling waters or in contact with the vapors of a cooling water systemcontaining the complex. It also demonstrates the stability of thecorrosion inhibitors of the present invention at elevated temperatures,over 300C, for extended periods of time.

In each of the following examples, the indicated polyamine and zinccompound are added to the aqueous corrosive medium so that 50 parts permillion of each IS present.

EXAMPLE VII Ingredients Parts Aqueous corrosive medium 75,000 PolyamineCompound No. l 2 Zinc sulfate 2 EXAMPLE VIII Ingredients Parts Aqueouscorrosive medium 80,000 Polyamine Compound No. 2 2.6 Zinc sulfate 2.6

EXAMPLE IX Ingredients Parts Aqueous corrosive medium 90,000 PolyamineCompound No. 6 2.3 Zinc sulfate 2.3

EXAMPLE X Ingredients Parts Aqueous corrosive medium 90,000 PolyamineCompound No. I3 2.3 Zinc sulfate 2.3

EXAMPLE XI Ingredients Parts Aqueous corrosive medium 90,000 PolyamineCompound No. 14 2.3 Zinc sulfate 2.3

EXAMPLE XII Ingredients Parts Aqueous corrosive medium 65,000 PolyamineCompound No. 18 1.6 Zinc sulfate 1.6

EXAMPLE XIII Ingredients Parts Aqueous corrosive medium 1 L000 PolyamineCompound No. 20 2.7 Zinc sulfate 2.7

EXAMPLE XIV lngrcdients Parts Aqueous corrosive medium 100,000 PolyamineCompound No. 22 2.5 Zinc sulfate 2.5

(The sodium salts of the above Compound Nos. 1, 2, 6, 13, 14 and 18 areused in place of the acid forms.) Tests 1 and 2 were conducted on eachof the abovetreated aqueous corrosive media. The corrosion rates in allinstances were lower than the untreated corrosive EXAMPLE XV Acompressed ball of a standard weight and dimension is preparedcontaining the following ingredients in the quantities noted.

Polyamine Compound No.

. 34 Lignosulfitc binder (bindarene) 8 Zinc sulfate l6 lnert Ingredients42 The above composition after briquetting is found suitable formechanically measured addition in water treatment wherein a ball feederis employed.

EXAMPLE XVI Example 1 (above) is repeated with the exception that coppercoupons are used instead of mild steel coupons and sufficient amounts ofl,2,3-benzotriazole to provide 1, 5 and ppm thereof in the corrosivemedia is used in addition to the polyamine. Example XVI is repeatedagain but without the benzotriazole material. The data shows that whencopper coupons are used and the corrosive media contains the indicatedpolyamine, the corrosion rates are less than when the corrosion mediadoes not contain saidpolyamine. The data further show that use of thebenzotriazole with the polyamine further reduces the corrosion rate.

it is also within the scope of the present invention to utilizesilicates, particularly inorganic silicates, in combination with thepolyamines. It is known that silicates are effective corrosioninhibitors as exemplified by Encyclopedia of Chemical Technology, Kirk-Othmer, 1961 by The lnterscience Encyclopedia, Inc. New York Volume 4,pages 487-529, and Volume 12, pages 268-360; this subject matter is tobe considered as incorporated herein by reference. (These silicates canbe used in the same concentration as the water-soluble zinc saltsheretofore mentioned.)

It is found in the repeat of the above Example I that the use of acombination of the indicated polyamine and a liquid (sodium) silicate(having a 3.22:1 ratio of SiO to soda) effected a lower corrosion ratethan either the polyamine per se or the silicate per se when usedseparately.

Thus, it may be seen that this invention relates to the indicatedpolyamines falling within Formula 1 above as corrosion inhibitors. We donot intend to be limited to any compounds, composition, or methodsdisclosed herein for illustrative purposes. Our invention may beotherwise practiced and embodied within the scope of the followingclaims.

What is claimed is:

1. A composition useful for inhibiting the corrosion of metals in awater system consisting essentially of from about 2% to about 80% byweight of a water solu ble zinc salt and from about 20% to 98% by weightof a polyamine having the general formula wherein (a) R,, R and R; arealike or unlike and are each selected from the group consisting of and Mis either hydrogen or any cation which will provide sufficientsolubility in said aqueous system; (b) R is an alkyl group containingfrom about 1 to 8 carbon atoms; (c) X and Y are each alike or unlike andare selected from the group consisting of hydrogen and alkyl; (d) n hasa value of from 1 through 15 and (e) mhas a value of from 1 through 20.

2. The composition as set forth in claim 1 wherein X and Y both arehydrogen.

3. The composition as set forth in claim 2 wherein R R and R are each CHCO M groups.

4. The composition as set forth in claim 2 wherein M is an ion selectedfrom the group consisting of alkali metals, ammonia, zinc, and mixturesthereof.

5. The composition as set forth in claim 4 wherein the water solublezinc salt is zinc sulfate and M is sodium.

6. The composition as set forth in claim 1 and addiw ts/.1. ...c...i

wherein (a) R R and R are alike or unlike and are each selected from thegroup consisting of and M is either hydrogen or any cation which willprovide sufficient solubility in said aqueous system; (b) R is an alkylgroup containing from about 1 to 8 carbon atoms; (c) X and Y are eachalike or unlike and are selected from the group consisting of hydrogenand alkyl; (d) n has a value of from 1 through l5 and (e) m has a valueof from 1 through 20; (2) from about 1% to about 10% by weight of acompound selected from the group consisting of 1,2,3 triazoles, thiolsof thiazoles, thiols of oxazoles, thiols of imidazoles, and mixturesthereof, and (3) up to about 79% by weight ofa water soluble zinc salt.

8. The composition as set forth in claim 7 wherein said polyamine isselected from the group consisting of Rll lolPHiof Ha CHIP 03H:

tionally containing a water-soluble hexavalent compound of chromium.

10. A method of inhibiting the corrosion of metals in a water systemcomprising maintaining in the water of said system at least 3 parts permillion of a polyamine having the general formula IlifXLP/in l O Rz LIin: [R Clin -(OM);

wherein (21) R R and R are alike or unlike and are each selected fromthe group consisting of X0 [434 iroM and lvfis either hydrogen oranycation which will provide sufficient solubility in said aqueoussystem; (b) R is an alkyl group containing from about 1 to 8 carbonatoms; (0) X and Y are each alike or unlike and are selected from thegroup consisting of hydrogen and alkyl; (d) n has a value of from 1through 15 and (e) m has a value of from 1 through 20.

1 1. The composition as set forth in claim 10 wherein X and Y both arehydrogen.

12. The composition as set forth in claim 11 wherein R R and R are eachCH CO M groups.

13. The composition as set forth in claim 11 wherein M is an ionselected from the group consisting of alkali metals, ammonia, zinc, andmixtures thereof.

14. The method as set forth in claim 10 and additionl H H H allycontaining in said system a water'soluble hexavalent compound ofchromium.

15. The method as set forth in claim 10 and additionally containing insaid system a water soluble zinc salt.

16. The method as set forth in claim 15 and additionally containing insaid system a water soluble hexavalent compound of chromium and a watersoluble zinc salt.

17. The method as set forth in claim 10 wherein said system containscuprous metals and the water system additionally contains a compoundselected from the group consisting of l,2,3 triazoles, thiols ofthiazoles, thiols of oxazoles, thiols of imidazoles, and mixturesthereof.

18. The method as set forth in claim 17 wherein the water systemadditionally contains a water soluble zinc salt.

19. A composition useful for inhibiting the corrosion of metals in awater system comprising from about 2% to about by weight of a silicateand from about 20% to about 98% by weight of a polyamine having thegeneral formula ugllii wherein (a) R,, R and R are alike or unlike andare each selected from the group consisting of a value of from 1 through20.

mg UNITED sums PATENT omen CERTIFICATE OF. CORRECTION Patent No.$816,333 ag June 11, 197 4 Inventor) Thomas M. King and Robert S.Mitchell It 10 certified thlt error appear. in the hm-14mm plan: andthat aid Lott-n Patent are hereby corrected as shown below:

On the title page, in Item 75, both inventors are from Missouri.

In the Table under Columns 3 and 4, R of Compound 20 should read -C H InClaims 1, 7, l0 and 19, the formula first appearing should read asfollows:

N M I N C N C N 1/ L \I 2 R Y n R Y n m CH P-(OM) and, two lines belowsaid formula, the expression C P OM Y OM should be deleted In Claim 8,the two formulas should read as follows:

1 n N (CH N (CH N CH CH PO H my UNITED STATES PATENT-OFFICE CERTIFICATEOF. CORRECTION Plcgnt N9. June 11,

unmet) Thomas M. King and Robert s. Mithell I: in run-4 thlt errornppnra 1n the abovn-idanciflcd panacand that aid Littlrl hum: an hat-bycon-mend u uhm'm bolaw:

N (cm N (an) N 2 6 6 CH PO 2 3 2 ,3 2

Signed and sealed this 1st day of Octobr 1974,

(SEAL) Attest:

MCCOY M. GIBSON JR.v C. MARSHALL DANN Attesting Officer Commissioner ofPatents page 2

2. The composition as set forth in claim 1 wherein X and Y both arehydrogen.
 3. The composition as set forth in claim 2 wherein R1, R2, andR4 are each -CH2CO2M groups.
 4. The composition as set forth in claim 2wherein M is an ion selected from the group consisting of alkali metals,ammonia, zinc, and mixtures thereof.
 5. The composition as set forth inclaim 4 wherein the water soluble zinc salt is zinc sulfate and M issodium.
 6. The composition as set forth in claim 1 and additionallycontaining a water-soluble hexavalent compound of chromium.
 7. Acomposition for inhibiting the corrosion of metals in a water systemwhich contains cuprous metals comprising (1) from about 20% to about 90%by weight of a polyamine having the general formula
 8. The compositionas set forth in claim 7 wherein said polyamine is selected from thegroup consisting of
 9. The composition as set forth in claim 7 andadditionally containing a water-soluble hexavalent compound of chromium.10. A method of inhibiting the corrosion of metals in a water systemcomprising maintaining in the water of said system at least 3 parts permillion of a polyamine having the general formula
 11. The composition asset forth in claim 10 wherein X and Y both are hydrogen.
 12. Thecomposition as set forth in claim 11 wherein R1, R2, and R4 are each-CH2CO2M groups.
 13. The composition as set forth in claim 11 wherein Mis an ion selected from the group consisting of alkali metals, ammonia,zinc, and mixtures thereof.
 14. The method as set forth in claim 10 andadditionally containing in said system a water soluble hexavalentcompound of chromium.
 15. The method as set forth in claim 10 andadditionally containing in said system a water soluble zinc salt. 16.The method as set forth in claim 15 and additionally containing in saidsystem a water soluble hexavalent compound of chromium and a watersoluble zinc salt.
 17. The method as set forth in claim 10 wherein saidsystem contains cuprous metals and the water system additionallycontains a compound selected from the group consisting of 1,2,3triazoles, thiols of thiazoles, thiols of oxazoles, thiols ofimidazoles, and mixtures thereof.
 18. The method as set forth in claim17 wherein the water system additionally contains a water soluble zincsalt.
 19. A composition useful for inhibiting the corrosion of metals ina water system comprising from about 2% to about 80% by weight of asilicate and from about 20% to about 98% by weight of a polyamine havingthe general formula